Add 'randomBoolean' doc page. (#530)

docs/blocks/math/random-boolean.md

@@ -0,0 +1,29 @@
+# random Boolean
+
+Returns a pseudo-random boolean value that is either `true` or `false`.
+
+```sig
+Math.randomBoolean()
+```
+
+## Returns
+
+* a pseudo-random [boolean](types/boolean) that is either `true` or `false`.
+
+## Example
+
+Make your @boardname@ do a coin toss when it's dropped softly. Have the LEDs show 'heads' or 'tails' as the result of the toss.
+
+```blocks
+input.onGesture(Gesture.FreeFall, () => {
+    if (Math.randomBoolean()) {
+        basic.showIcon(IconNames.Happy)
+    } else {
+        basic.showIcon(IconNames.Sword)
+    }
+})
+```
+
+## See Also
+
+[random](/reference/math/random)